As benzopyran derivatives, 4-acylaminobenzopyran derivatives exemplified by Cromakalim have been known (for example, Japanese Patent Laid-open No. Sho 58-67683). These 4-acylaminobenzopyran derivatives exemplified by Cromakalim are known to open ATP sensitive K+ channel so as to be effective for the treatment of hypertension and asthma, but there has not been any mention as to the treatment of arrhythmia based on the prolongation effect on the refractory period.
In addition, it is reported that 4-aminobenzopyran derivatives that have β3-receptor stimulating action and are supposed to be effective for the treatment of obesity (for example, WO 03/014113), but there has not been any mention as to the treatment of arrhythmia based on the prolongation effect on the refractory period this document.